ES6 Group By和SUM的实现
问题描述：
我有一个具有以下属性的对象数组:material_no，material_name，qty.
I have an array of objects with these properties: material_no, material_name, qty.
let data = [
{ material_no: '1001', material_name: 'Material 1', qty: 100 },
{ material_no: '1001', material_name: 'Material 1', qty: 50 },
{ material_no: '1002', material_name: 'Material 2', qty: 44 },
{ material_no: '1003', material_name: 'Material 3', qty: 125 },
{ material_no: '1002', material_name: 'Material 2', qty: 59 },
{ material_no: '1004', material_name: 'Material 4', qty: 999 },
{ material_no: '1005', material_name: 'Material 5', qty: 80 },
{ material_no: '1005', material_name: 'Material 5', qty: 66 }
]
如何返回按其material_no/material_name和具有相同material_no/material_name的数量的总和分组的对象数组?
How do I return an array of objects grouped by their material_no/material_name and sum of the qty having the same material_no/material_name?
[
{ material_no: '1001', material_name: 'Material 1', qty: 150 },
{ material_no: '1002', material_name: 'Material 2', qty: 103 },
{ material_no: '1003', material_name: 'Material 3', qty: 125 },
{ material_no: '1004', material_name: 'Material 4', qty: 999 },
{ material_no: '1005', material_name: 'Material 5', qty: 146 }
]
答
您可以将数组简化为 Map ，按 material_no 存储总项.然后只需将映射值提取到数组即可.
You could reduce array to a Map that stores total items by material_no. And then just extract map values to array.
let data = [
{ material_no: '1001', material_name: 'Material 1', qty: 100 },
{ material_no: '1001', material_name: 'Material 1', qty: 50 },
{ material_no: '1002', material_name: 'Material 2', qty: 44 },
{ material_no: '1003', material_name: 'Material 3', qty: 125 },
{ material_no: '1002', material_name: 'Material 2', qty: 59 },
{ material_no: '1004', material_name: 'Material 4', qty: 999 },
{ material_no: '1005', material_name: 'Material 5', qty: 80 },
{ material_no: '1005', material_name: 'Material 5', qty: 66 }
]
const sums = [
...data.reduce(
(map, item) => {
const { material_no: key, qty } = item;
const prev = map.get(key);
if(prev) {
prev.qty += qty
} else {
map.set(key, Object.assign({}, item))
}
return map
},
new Map()
).values()
]
console.log(sums)